Secrecy performance analysis of cooperative multiuser single carrier systems

In this paper, we study the secrecy performance of cooperative single carrier system with the kth-best user selection scheme in Rayleigh fading channels. Assuming perfect decoding at the relay, we choose the legitimate user with the kth-best instantaneous signal-to-noise ratio (SNR) among Q users to receive the forwarded messages, which are intercepted at a passive eavesdropper simultaneously. To accurately assess the secrecy performance of the system, we derive exact closed-form expressions of secrecy outage probability and the probability of nonzero secrecy capacity to evaluate the impact of key parameters on the secrecy performance. Moreover, the asymptotic analysis is also performed to demonstrate that the secrecy diversity order is determined by both the number of channel taps and the index of the selected user. Finally, simulation results are provided to verify the correctness of the derived closed-form as well as asymptotic expressions.